Depression and grief can feel identical to one another. There is sadness, loss of attention and concentration, decreased memory functioning, and changes in sleep, appetite, and sex drive. Things that used to provide enjoyment no longer do. It's hard to think about anything or anyone else in the midst of this kind of state. It hurts terribly and daily functioning can be profoundly affected.
But, there are also some key differences between depression and grief. Grief is triggered by an identifiable loss that could reasonably be expected to trigger loss and sadness in most people. The death of a loved one; the loss of a job; a job transfer and your child has to move from the only home that she/ he knew; a major financial set back; divorce - these are all significant losses that can trigger grief. But, people who are grieving have a sense that they are going to get over the loss eventually. And, usually outside of the specific loss, people who are grieiving can still appreciate other people and things in their life. I often 'prescribe' to my patients who are grieving, to take days off from the grieving to do more replinishing things. When tempted to grieve on the 'off' days, they can save the material for their next 'grieving day.' Grieving rarely lasts more than a month or two, and the worst of the grief starts to fade typically sooner than this.
Depression is a different phenomenon. It may or may not be triggered by an identifiable loss. People with clinical depression may not feel like they are ever going to get over it. As one of my depressed patients said to me: "When you are down in the dumps, it's like you're having a bad day. But when I'm depressed, I feel like I'm having a bad life." People who are depressed don't just snap out of it. There's no taking a day off from depression to focus on more replenishing things. There is a higher level of self absorption. Nothing feels good, tastes good, or is gratifying. Depression is often accompanied by suicidal thoughts; this is rarely true of grief (a grivieng person may want to be heaven with a lost loved one, but this is different than saying that they want to kill themselves to end their own suffering).
Grief goes away on its own and the worst of it goes away withing a week or two of the loss. Depression tends to linger. If the low mood is persisting, it's time to get a professional consultation to figure if it's depression or grief. Skilled and caring professionals are availble in the Chicago area at http://www.heritageprofessional.com. Otherwise, ask a trusted friend, pastor, or physician for a referral to a mental health professional for assistance.